Getting positive results with negative ions

Jul 18, 2011
Julia Laskin and Grant Johnson from Pacific Northwest National Laboratory and scientists from OI Analytical used a mass-selected ion deposition instrument to determine if the IonCCD™ can detect negative ions and large ions.

Yes! That's the answer scientists from OI Analytical and Pacific Northwest National Laboratory got from their experiments to see if the new IonCCDTM can detect negative ions and large ions. Furthermore, employing instruments at EMSL, the team used the detector to characterize the ion beam inside a mass spectrometer, a workhorse instrument for basic energy research. The results grace the cover of the Journal of the American Society for Mass Spectrometry.

While most scientists think of mass spectrometers as analytical tools that enable characterization of proteins, pollutants and other molecules, mass spectrometers may also be used to create materials. For example, researchers are using the instruments to prepare novel catalysts that increase the efficiency of chemical reactions (see related articles). To build tailored materials, these special mass spectrometers deposit layers of specific ions onto a surface. With the IonCCD's ability to directly visualize the ion beam, scientists can produce beams of ions with narrow diameters, and thus design instruments that more precisely create materials.

"We were excited," said Dr. Julia Laskin, who led the research at PNNL. "With the IonCCD, you can visualize ion beams, whether they are at or high vacuum."

To test the IonCCD, the team began with a mass-selected ion deposition instrument, built by Laskin and her team at EMSL, a national scientific user facility. The team placed the IonCCD inside the deposition instrument that produces beams of ions. The IonCCD, using a pixel-based detector array, accumulates the charge of the ions on its surface. The charge is then dumped onto a waiting , where it is detected.

When negative ions were sent to the IonCCD, it correctly measured them. When large ions, positive or negative, were fed through the detector, it again gave the desired response.

In addition to the detection work, the team also explored visualizing ion beams inside the ion deposition instrument. This work was the subject of a second publication in the Journal of the American Society for Mass Spectrometry. Scientists usually rely on phosphor screen detectors to visualize ion beams. These detectors only work under vacuum due to the high voltages they require. So, if the ion beam is at high gas pressure the phosphor screen detectors don't work. Further, conventional detectors are bulky and, therefore, often provide a limited view of the ion beam because of the spatial confinements of a vacuum chamber. With the small-sized IonCCD detector, scientists can see what are in the beam and how they are moving throughout an entire mass spectrometer system. Such information may be used to improve the design and construction of these instruments.

The researchers are determining if the IonCCD can detect charged droplets in the . Droplets in the early stages of an electrospray cause signal to drop and provide poor results.

Explore further: Superconducting circuits, simplified

More information: Hadjar O, et al.  2011. "IonCCDTM for Direct Position-Sensitive Charged-Particle Detection: From Electrons and keV Ions to Hyperthermal Biomolecular Ions." Journal of the American Society of Mass Spectrometry 22, 612-623. DOI: 10.1007/s13361-010-0067-7

Johnson GE, et al. 2011. "Characterization of the Ion Beam Focusing in a Mass Spectrometer Using an IonCCDTM Detector" Journal of the American Society of Mass Spectrometry. DOI: 10.1007/s13361-011-0154-4.

The research was done in EMSL, a national scientific user facility at PNNL.

add to favorites email to friend print save as pdf

Related Stories

Separating the Catalysts from the Chaff

Sep 09, 2010

When studying how specific catalysts drive reactions, scientists are often frustrated by the actions of unrelated molecules in the samples. Now, thanks to a device created by a team at Pacific Northwest National ...

Invention could aid Mars probes' search for life

Aug 16, 2010

The next generation of Mars rovers could have smaller, cheaper, more robust and more sensitive life-detecting instruments, thanks to a new invention by scientists at DOE's Idaho National Laboratory.

Carnegie Mellon scientist to build unique mass spectrometer

Jan 11, 2006

Carnegie Mellon University's Mark Bier has received a $546,000 grant from the National Science Foundation's Instrument Development for Biological Research program to build a heavy-ion mass spectrometer. This one-of-a-kind ...

Recommended for you

Superconducting circuits, simplified

Oct 17, 2014

Computer chips with superconducting circuits—circuits with zero electrical resistance—would be 50 to 100 times as energy-efficient as today's chips, an attractive trait given the increasing power consumption ...

Protons hog the momentum in neutron-rich nuclei

Oct 16, 2014

Like dancers swirling on the dance floor with bystanders looking on, protons and neutrons that have briefly paired up in the nucleus have higher-average momentum, leaving less for non-paired nucleons. Using ...

Cosmic jets of young stars formed by magnetic fields

Oct 16, 2014

Astrophysical jets are counted among our Universe's most spectacular phenomena: From the centers of black holes, quasars, or protostars, these rays of matter sometimes protrude several light years into space. ...

User comments : 0